1. Field of the Invention
The present invention relates to a method of controlling a terminal of an MPEG-4 (Moving Picture Experts Group-4) system, and more particularly, to a method of controlling an MPEG-4 system using a caching mechanism to more rapidly reproduce the contents at a client side.
2. Description of the Related Art
MPEG-4 (Moving Picture Experts Group-4) is a technical standardization organization which relates to moving pictures and related audio signal compression and reproduction and which operates under the name of “WG11 (Working Group 11)” in the “SC29 (Sub-Committee 29)”. Here, the “SC29” is an organization to establish the international standards of the multimedia related coding mechanisms under the JTC (Joint Technical Committee), which is jointly established by the International Standardization Organization (ISO) and the International Electrotechnical Conference.
Related to the MPEG-4 standard, there are technical standards regarding the moving picture and the moving picture related audio signal compression and reproduction such as the MPEG-1 and MPEG-2 standards. In the MPEG-1 and MPEG-2 standards, a sending end compresses the moving picture and speech information as input in a random volume according to the determined data throughput, and transmits the compressed moving picture and speech information in a bit stream. Then, a receiving end decodes the original moving picture and speech information from the bit stream and outputs the decoded moving picture and speech information on a screen or through a speaker.
The MPEG-4 standard is different from the MPEG-1 and MPEG-2 standards with respect to the input source. Specifically, one content consists of a number of objects. Here, the objects are an audio stream, a visual stream, a scene description stream and an object descriptor stream. Therefore, a screen consists of the scene descriptor object to constitute the screen, the object descriptor object to connect the scene descriptor to the audio and visual streams, and the audio and visual stream object to be displayed on the screen.
Further, the MPEG-4 standard is constituted so that a synthetic picture, such as computer graphics or three-dimensional data (facial animation), and synthetic sound information, such as MIDI, TTS (Text-To-Speech), are processed together. The existing standards are provided on condition that any determined technique should be designed in a semiconductor chip and manufactured in a system. However, the MPEG-4 standard develops a number of tools to perform various functions and allows a flexibility to combine the tools freely if necessary and to realize any desired functions.
The unique feature of the MPEG-4 standard is to concentrate the utmost effort on an error correction coding mechanism since, at the outset, it was assumed that the MPEG-4 standard would be applied in mobile communication systems. Based on the above-mentioned feature, the system group has adopted the multiplexing mode and the synchronizing mode to control the bit stream according to the data service between the system and the network.
The main fields of application of the above-developed technology are, for example, multimedia data services of a portable device, Internet services, remote medical and educational systems, Interactive TV, Interactive game machines and digital video discs (DVD).
FIG. 1 is a block diagram illustrating a process of reproducing the contents in a conventional MPEG-4 system terminal. A terminal of a client side is connected to a server, and an interface between the server and the basic contents information is performed (S1). When a command to reproduce the contents is input in the terminal of the client side by a user (S2), the client terminal requests from the server an initial object descriptor (IOD) (S3). If the IOD is received (S4), the IOD is parsed in the client terminal (S5). As a result of parsing, it is determined whether the binary format scene for description (BIFS) streaming, the object description (OD) streaming, the visual streaming and/or the audio streaming are required (S6). If the object data streaming is required, the necessary object data is requested to the server (S7). When the object data requested to the server is received (S8) and if the received data is the BIFS or OD, the terminal parses each of the BIFS and OD (S9) and re-performs the operation S6. If any further streaming of the object data is not required, the reproduction of the contents is ended. Otherwise, if the data received in the terminal is neither BIFS nor OD, the received object data is reproduced (S10). Further, if there exists any further object data to be received, the necessary object data is requested to the server (S7). However, if there is no more object data to be received, the reproduction of the contents is ended (S12).
However, in the terminal of the above-mentioned MPEG-4 system, since the object data is provided by the server side in response to the request from the client side, there is the problem that it takes a slightly longer time until the contents are reproduced. In other words, when the requested contents consists of a number of objects, the server transmits each object through the streaming mode to the client. In this connection, the time for the client to request the object data from the server and the time required until the response from the server is transmitted are additionally required and, as a consequence, it takes a slightly longer time until the contents are reproduced.
Moreover, when a number of objects are requested at the same time, there is the other problem of causing any overload in the network and system.